Within the field of neurotechnology, deep brain stimulation (DBS) is a surgical treatment involving the implantation of a medical device called a deep-brain stimulator, which sends electrical impulses to specific parts of the brain. DBS in certain brain regions has provided remarkable therapeutic benefits for otherwise treatment-resistant disorders such as chronic pain, Parkinson's disease, tremor and dystonia. Despite the long history of DBS, its underlying principles and mechanisms are still not clear. DBS directly changes brain activity in a controlled manner. Unlike lesioning techniques, its effects are reversible. Furthermore, DBS is one of only a few neurosurgical methods that allow blinded studies.
In principle, the deep brain stimulation system comprises two components: the implanted pulse generator (IPG), and the probe. The IPG is a battery-powered neuro stimulator that sends electrical pulses to the brain to interfere with neural activity at the target site. The IPG is typically encased in e.g. a titanium housing. The probe consists of about 10-40 cm long wires and a plurality of electrodes. The wires connect the IPG to the electrodes, which are located at the distal end of the probe. The IPG may be calibrated by a neurologist, nurse or trained technician to optimize symptom suppression and control side effects.
DBS probes are placed in the brain according to the type of symptoms to be addressed. All components are surgically implanted inside the body. The typical procedure is performed under local anaesthesia, where a hole is drilled in the skull and the electrode is inserted with feedback from the patient for optimal placement. The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa.
Commercially available DBS systems consist of a chest-implanted IPG, a connector cable of approximately 30 cm running subcutaneously from the IPG to the top of the patient's head, and a lead cable connected proximally to the connector cable by means of a connector, which may be approximately 20 mm long and 4-5 mm in diameter. The lead cable carries 4 electrodes distally, and is itself rather long, around 30 cm, so that a lot of excess length has to be left under the patient's scalp. This system has several disadvantages:
the fixation of the lead cable is difficult and it is liable to lead displacement and inaccuracies;
the long cables cause irritation and erosion of the skin;
the cables are the source of lead break;
infection can propagate subcutaneously along the cable into the brain; and
the long and uncontrolled cable bundles give rise to potentially dangerous voltages when submitted to the electromagnetic fields of a Magnetic Resonance Imaging scanner (MRI).
US 2005/0,228,249 proposes solutions to the afore-mentioned by providing an IPG mounted in a ferrule, intracranially after a craniotomy is performed in the parietal bone, with the IPG device mounted into the ferrule, and further connected to seed electrodes by means of a seed electrode interface that can have the shape of a burrhole cover, or be simply a subcutaneous module.
However, this solution still needs cables running subcutaneously, to cranial positions, possibly quite remote from the parietal position of the ferrule-mounted IPG. This may give rise to unwanted motion of the wire, which lead to mechanical forces on the probe and thus potential damage to brain tissue. Also, the probe wire must have extra length to allow manipulation of the implantable device before the implantation. When this excess wire is stored subcutaneously after placement of the probe, it may lead to irritation, skin erosion, and potentially infection.
Hence, an improved way of mounting a DBS probe, allowing for increased flexibility, cost-effectiveness, safety and user friendliness would be advantageous.